Expandable Surgical Access Port with Elongated Workspace

This application is a continuation-in-part of U.S. application Ser. No. 18/217,089 filed on Jun. 30, 2023, which claims the benefit of U.S. Provisional Application No. 63/358,651 filed on Jul. 6, 2022, the entire contents of both of which are incorporated herein by reference.

A variety of access ports have been proposed and used for accessing the delicate tissue of the brain. Accessing brain tissue, especially interior brain tissue that is not accessible at the surface, poses a variety of challenges. For example, it is desirable to minimize damage to the brain tissue by a traumatically forming a pathway for access. To this end, surgical access ports typically have a tapered distal end to gently spread the tissue as the access port is moved into position at the surgery site. Upon reaching the surgery site, the central portion of the access port is removed or the access port is expanded to form a pathway for surgical instruments.

Another challenge with brain access ports is that the brain tissue can be damaged simply by contact with the wall of the access port. Intracranial pressure causes the brain tissue local to the access port to compress, potentially leading to brain ischemia—i.e., a reduction in blood flow and oxygen that can potentially lead to death of the local brain tissue. Such damage was particularly likely in the past, when flat blade or spoon retractors were used to create a surgical access pathway. The change to access ports having a full circular or oval shape has helped reduce the likelihood of ischemia, but this risk still remains under any circumstance in which the brain tissue is compressed.

While various brain access ports are known, there is an ongoing need to improve the art of surgical access ports.

In one exemplary aspect, there is provided an expandable surgical access port having an arm mounting body, a number of primary arms, a number of secondary arms, an activation ring, and an expandable membrane. The arm mounting body defines an arm mounting body opening surrounding a longitudinal axis, and the arm mounting body has a number of primary pivot locations surrounding the longitudinal axis and fixed at a respective first pivot location distance from the longitudinal axis, and a number of secondary pivot locations surrounding the longitudinal axis and fixed at a respective second pivot location distance from the longitudinal axis. The primary arms are arranged around the longitudinal axis, and each primary arm is pivotally attached at a respective primary pivot location and extends in a distal direction along the longitudinal axis to a respective primary arm distal end. The secondary arms are arranged around the longitudinal axis, and each secondary arm is pivotally attached at a respective secondary pivot location and extends in the distal direction along the longitudinal axis to a respective secondary arm distal end. The activation ring is rotatably mounted to the arm mounting body to rotate about the longitudinal axis between a first activation ring position and a second activation ring position. The activation ring has: a number of primary cam surfaces configured to each engage a respective primary arm to drive the respective primary arm from a respective closed position in which the respective primary arm distal end is a respective first arm distance from the longitudinal axis to a respective open position in which the respective primary arm distal end is a respective second arm distance from the longitudinal axis, upon movement of the activation ring from the first activation ring position to the second activation ring position, and a number of secondary cam surfaces configured to each engage a respective secondary arm to drive the respective secondary arm from a respective closed position in which the respective secondary arm distal end is a respective third arm distance from the longitudinal axis to a respective open position in which the respective secondary arm distal end is a respective fourth arm distance from the longitudinal axis, upon movement of the activation ring from the first activation ring position to the second activation ring position. The respective fourth arm distance of each secondary arm distal end is greater than the respective second arm distance of each primary arm distal end. The expandable membrane extends from a proximal membrane position, to a distal membrane position adjacent to each primary arm distal end and each secondary arm distal end. When the activation ring is in at least the second activation ring position, an entirety of the expandable membrane between the proximal membrane position and the distal membrane position comprises an elongated membrane cross-section as viewed along the longitudinal axis, the elongated membrane cross-section extending along a major membrane axis and a minor membrane axis perpendicular to the major membrane axis.

In the drawings, features that are repeated in substantially identical form are in many cases designated at a single location within the drawings to preserve the clarity of the drawings. Like features are designated in different embodiments with like reference numbers.

The present disclosure provides non-limiting examples of embodiments of expandable brain access ports. Specific details of these embodiments are provided to aid in understanding, but such details are not intended to limit the scope of any of the appended claims, except as specifically recited in the claims. It will also be understood that certain details not currently recited in the claims may be added to the claims in the future, particularly as it becomes apparent through consideration of prior art and other factors that these details provide a benefit over the known art.

A first example of an expandable access portis shown in. The expandable access portgenerally includes an activation assembly, and expandable port, and an introducer. Details of these features are discussed below. The expandable access portis configured to hold or provide access for one or more surgical instruments, such as endoscopes, resection tools, suction hoses, lights, and navigation devices. To this end, the activation assemblydefines an activation assembly openingthat surrounds a longitudinal axisof the expandable access port.

In the case of, the expandable access portis set up in a configuration to hold a navigation probelocated internal to the expandable access port. The navigation probeis connected to a tracking system that monitors the position of the navigation probe. A typical navigation probeand tracking system are registered to track the position of the probe's tipand the trajectory of the probe shaft. When integrated into the expandable access port, the probe tipmay be located at the distal tip of the introducerto simply use the pre-set registration of the navigation probeto track the introducer tip, and thus assume or extrapolate the position of the remainder of the expandable access port. It is also possible to register the navigation probeto track the full shape and position of the expandable access port, regardless of the actual position of the probe tipand probe shaftFor example, if the probe tipis seated a certain fixed distance from the distal end of the introducer, an offset can be programmed into the tracking system to account for this known offset. It is also possible to register the exact shape of the expandable access portand/or the expandable port, to track the entire shape of device. Such navigation probesand their tracking systems, including methods for setting an offset and determining the shape of the device, are known in the art, and need not be described in detail herein.

A probe lockis provided to selectively hold the navigation probeat a fixed location relative to the expandable access port. A non-limiting example of a suitable probe lockmay be found in U.S. application Ser. No. 17/473,282 (publication no. 2021/0401457), which is incorporated by reference herein. Other examples and details of probe locksare provided below.

In use, the activation assemblyand expandable portmay be provided as an assembled structure that is not generally intended for disassembly (e.g., no reversible fasteners such as screws), but this is not strictly required. The introducercan be secured to the activation assemblyand expandable portto facilitate atraumatic insertion of the expandable access portinto the brain to the surgery site. The navigation probemay be used to help direct the expandable access portprecisely to the surgery site. Upon insertion to the desired location, the introduceris removed, and the activation assemblyis operated to expand the expandable port. At the conclusion of surgery, the expandable access portis withdrawn from the brain. The expandable portmay or may not be retracted prior to withdrawing the expandable access port.

show another embodiment of an expandable access port, which is similar to the embodiment of, but with certain alternative structures as described below.show the expandable access portwith the expandable portin the contracted position, andshow the expandable portin the expanded position. In both cases, the introduceris assembled to the remainder of the expandable access port. As shown in, the expandable portextends along the longitudinal axisin a distal direction D from the activation assembly. To help in explaining features herein,also illustrates a proximal direction P, which is opposite the distal direction D.

also shows a navigation probein place inside the introducer, and a guidance armmounted to the activation assembly. The guidance armalso serves as a tracking device to directly monitor the position of the expandable access portafter the navigation probeis removed, or if the device is used without a navigation probe. Details of the guidance armare provided below.

An exemplary embodiment of an activation assemblyis shown in. The activation assemblygenerally includes a port housingand a lock ringthat are assembled together to form an activation arm mounting body, and an activation ringthat is movably mounted to the activation arm mounting body. The port housingdefines a port housing openingthe lock ringdefines a lock ring openingand the activation ringdefines an activation ring opening. The port housing openinglock ring openingand activation ring openingare aligned, and each surrounds or defines at least a portion of the activation assembly opening

In this example, the activation ringis rotationally mounted to the activation arm mounting body, such as explained below, such that the activation ringcan be rotated relative to the activation arm mounting body and about the longitudinal axis, between a first activation ring position and a second activation ring position. The first activation ring position is shown in, and in this position the expandable portis in the contracted position. The second activation ring position is shown inand in this position the expandable portis in the expanded position.

As best shown in, the port housingcomprises a generally ring-shaped structure that defines the port housing openingThe port housingincludes a plurality of first pivot recessesthat surround the longitudinal axisSimilarly, the lock ringis a generally ring-shaped structure that defines the lock ring openingand includes a plurality of second pivot recessesthat surround the longitudinal axisThe port housingand lock ringare secured together, such that the first pivot recessesand second pivot recessescollectively form cavities that each define a respective pivot locations(see). The pivot locationsmay be cylindrical (as shown), spherical, or have any other shape suitable to hold a corresponding pivot to rotate about a fixed axis. The pivot locationsare distributed around the longitudinal axisand each defines a respective pivot axis(see). The pivot axeslie in a common plane that is perpendicular to the longitudinal axis. The pivot axesare oriented such that they do not intersect the longitudinal axisEach pivot axisalso preferably extends tangentially to the longitudinal axis(i.e., tangential to an imaginary circle having its center at the longitudinal axiswith each pivot axisbeing equidistant at its closest location to the longitudinal axisThe pivot axesalso may be equidistantly positioned in the circumferential direction, such as shown in, which show six pivot axesspaced at angles of 60° about the longitudinal axis

The lock ringis secured to the port housingby any suitable means. For example, the lock ringis secured to the port housingby locking tabsthat snap into respective locking tab receiverspreferably in a manner that does not readily facilitate disconnection. In the illustrated example, the locking tabsare provided on the lock ring, and the locking tab receiversare provided on the port housing, but this arrangement may be reversed in whole or in part (i.e., one more of the locking tab receiversmay be on the lock ring, and one or more of the locking tabsmay be on the port housing). In other cases, the lock ringand port housingmay be connected by adhesives, ultrasonic welding, rivets, reversible mechanical fasteners (e.g., screws), and so on.

The port housingand/or lock ringmay include supplemental structures to increase their utility. For example, the port housingmay include one or more extensionsto which the introducerand accessories (surgical tools, navigation devices, etc.) may be mounted. The extensionsalso may be configured to secure to a clamp to hold the expandable access portat a fixed location relative to the patient, operating table or surgical frame. Each extensionmay include a lock mechanismor be shaped to connect to a lock provided on a different part. The details of such locks are not the subject of this disclosure, are well known in the art, and need not be described herein.

The activation arm mounting body (the connected port housingand lock ring) may include multiple extensions(e.g., two to four extensions). The extensionsalso may be arranged on one side of the activation arm mounting body (i.e., all within a 180° segment, or more preferably a 90° segment, about the longitudinal axis). This provides greater access for the surgeon to operate without obstruction on the other side of the activation arm mounting body.

As noted above, the activation ringis secured to the activation arm mounting body to rotate about the longitudinal axisrelative to the activation arm mounting body. In this example, the port housingincludes a plurality of sliding tabsthat snap into corresponding sliding tab receiversin the activation ring. Each sliding tab receivercomprises a circumferential slot having a relatively narrow width in the radial direction, and an end portion having a somewhat larger width in the radial direction. Each sliding tabterminates at a hook that can be inserted into the wide end portion of each sliding tab receiverand then slid along the narrow portion of the sliding tab receiverto rotate the activation ringrelative to the port housing. A hook or protrusion (not shown) may be provided between the wide and narrow portions of each sliding tab receiverto prevent the respective sliding tabfrom returning to the wide portion of the sliding tab receiverThus, the parts cannot be disassembled accidentally during use, and more preferably cannot be disassembled under any normal circumstances (e.g., without breaking the parts).

In the illustrated example, the sliding tabsare provided on the port housing, and the sliding tab receiversare provided on the activation ring, but this arrangement may be reversed in whole or in part (i.e., one more of the sliding tabsmay be on the activation ring, and one or more of the sliding tab receiversmay be on the port housing). Also, the sliding tabsand/or sliding tab receiversmay be provided on the lock ring, rather than the port housing.

In other embodiments, the activation ringmay be rotationally fixed to the activation arm mounting body using other connections. For example, the activation ringmay be captured in place against the activation arm mounting body by a central locking ring that threads into the activation arm mounting body. As another example, pins or screws may be inserted through the sliding tab receiversand secured to the activation arm mounting body to capture the activation ringin place. Other alternatives and embodiments will be apparent to persons of ordinary skill in the art in view of the present disclosure.

In still other embodiments, the activation ringmay be mounted to the activation arm mounting body move in other directions rather than the rotation described above. For example, the activation ringmay be mounted on rails to slide laterally relative to the activation arm mounting body.

Referring to(as an example), the activation ringpreferably is located on the proximal side of the port housing. This allows unhindered access to the activation ringwhen the activation arm mounting body is secured in place at the surgery site. Furthermore, the arrangement of sliding tabsand sliding tab receiversallows the activation ringto rotate relative to the activation arm mounting body throughout its entire operative range of motion while remaining at a fixed location along the longitudinal axis longitudinal axisThis arrangement minimizes the overall length of the expandable access port, and prevents the possible creation of unwanted axial forces along the longitudinal axisas the activation ringis rotated relative to the activation arm mounting body. While preferred, this arrangement is not required in all embodiments.

As also shown in, the activation ringmay have an outer surface defining a gripand the gripoptionally may be larger in diameter than an adjacent portion of the activation arm mounting body. This also facilitates ease of use, by providing a tactile distinction between the activation ringand activation arm mounting body, and helping to ensure that rotational forces are not erroneously applied to the activation arm mounting body during operation, and increasing the surgeon's ability to firmly hold the activation ring.

As shown in, one or more of the extensionsmay extend to be positioned at, or spaced in the proximal direction from, a proximal sideof the activation ring. For example, one or more of the extensionsmay be secured to the ring-like portion of the port housingvia an extension basethat extends in the proximal direction P. This arrangement makes the extensionsmore accessible for connecting to accessories and position locks, and allows the expandable portto be positioned deeper in the brain.

Referring to, the activation assemblymay include an activation ring coverthat covers the proximal sideof the activation ring. The activation ring coverencloses the proximal sides of the sliding tab receiverto prevent ingress of liquids or other matter that might obstruct operation of the activation ring. The activation ring coverhas an activation ring cover openingthat is concentric with the activation ring openingAs best shown in, the activation ringmay define a first tapered inlet surfaceand the activation ring covermay define a second tapered inlet surfacethat align to form a continuous tapered entry to the activation assembly openingthat decreases in diameter in the distal direction D. The activation ring covermay be secured to activation ringby any means, such as adhesives, snap fitment, ultrasonic welding, and so on. In this example, the activation ring coverhas pinsthat are secured into holes(see Figure in the adjacent face of the activation ring. One or all of the activation ring cover, first tapered inlet surfaceand activation ring cover openingalso may be omitted.

Details of the expandable portare now described in relation to. The expandable portgenerally includes a plurality of activation armsand a membrane.

Each activation armcomprises an elongated bodythat extends in the distal direction D from a respective proximal arm endto a respective distal arm endThe proximal arm endof each activation armis pivotally attached to the activation arm mounting body by a respective pivotIn this example, each pivotcomprises a cylindrical body that is captured in place at a respective pivot locationand extends along the respective pivot axiswhen the activation armis assembled to the activation arm mounting body (i.e., when the pivotis captured between a respective first pivot recessesand a respective second pivot recess). This allows the activation armpivot about a respective pivot axisIn other cases, the pivotsmay comprise spherical bodies, pins that are provided separately and inserted through holes in the activation arm, and so on.

Each activation armis pivotable between a first arm position, in which the distal arm endis a first distance Dfrom the longitudinal axis(see), and a second arm position, in which the distal arm endis a second distance Dfrom the longitudinal axis(see). The second distance Dis greater in magnitude than the first distance D. The activation ringis operable to move the activation armsbetween their respective first and second arm position. More specifically, the activation ringis rotatable between a first activation ring position in which the activation armsare in their first arm positions, and a second activation ring position in which the activation armsare in their second arm positions.

The activation armspreferably cannot be moved any closer together than the first distance D, so as to prevent the activation armsfrom pinching brain tissue when the activation armsare contracted without the presence of the introducer. This may be achieved, for example, by configuring the activation ringsuch that it cannot move the activation armsinwardly beyond the first position, by providing travel stops that contact the activation arms, or by making the activation arms such that they converge to contact each other along their circumferential sides in the first position. Other alternatives and embodiments will be apparent to persons of ordinary skill in the art in view of the present disclosure.

In this example, the activation ringmoves the activation armsby engagement between respective cam slotsin the activation ring, and respective cam followersat the proximal arm endsof each slotAs shown in, the cam slotsare formed as recesses in the lower face of the activation ring. As the name suggests, each cam slotis formed as an eccentric ramp about the longitudinal axisSpecifically, each cam slotextends about a portion of the activation ring openingfrom a respective first cam slot end′ to a respective second cam slot end″, and each respective second cam slot end″ is closer to the longitudinal axisthan each respective first cam slot end′. The portion of the cam slotbetween the first cam slot end′ and the second cam slot end″ may be straight, arced (shown) or have any other smooth continuous shape that performs the function described herein.

Each cam followerextends into a respective one of the cam slotsand rotating the activation ringrelative to the activation arm mounting body causes the cam slotsto drive the respective cam followertowards or away from the longitudinal axisdepending on the direction of rotation. In this case, each activation armacts as a class 1 lever, with the pivotlocated between the cam followerand the distal arm endThus, when the cam followersare located at the first cam slot ends′ the distal arm endsare located in their respective first arm positions to contract the expandable port, and when the cam followersare located at the second cam slot ends′ the distal arm endsare located at their respective second arm positions to expand the expandable port. The cam slotsmay include protrusions (not shown) that extend inwardly to provide one or more locations at which movement of the respective cam followersis inhibited without applying a somewhat greater torque to the activation ring. Such protrusions can be positioned to establish predefined locations at which the activation armsare held at one or more positions. For example, a protrusion may be provided to hold the activation armsat their respective first or second positions, or anywhere between. Such protrusions can help the surgeon feel where the determined locations are. Other shapes, such as bends in the cam slotscan be provided to serve the same function.

The cam slotsmay be shaped such that the cam followerscannot back-drive the activation ring. Specifically, the angle of contact between the cam followersand cam slotsmay be selected such that a force applied to rotate the armgenerates a frictional load that prevents relative motion between the parts. This angle can be determined using conventional engineering principles (e.g., static coefficient of friction of an object on a ramp), and need not be describe in further detail herein.

The cam slotsalso may be shaped to capture both sides the cam followerssuch that the armscannot move freely in either direction. This prevents the armsfrom moving beyond the position dictated by one side of the cam slot surface, and provides precise control of the arms' positions when rotating the activation ringin alternating directions. This is expected to be beneficial to allow the surgeon to apply driving forces to precisely open and close the arms, preferably to any desired position, without relying on resilient forces (e.g., pressure from brain tissue) to collapse the armswhen it is desired to retract the arms. The cam slotspreferably also are configured to prevent the activation ringfrom being moved to drive the activation armsbeyond their respective first position, such as by terminating each cam slotat a closed end that stops on the cam follower

In other embodiments, the activation ringcan be configured to operate as a class 2 lever on the activation arms. For example, the cam slotsand cam followersmay be located between the pivotand distal arm endof each. Other alternatives and embodiments will be apparent to persons of ordinary skill in the art in view of the present disclosure.

The activation arm mounting body is configured to permit engagement between the cam slotsand cam followerssuch as by including a respective cam follower portpassing through the lock ringto a proximal sideof the lock ringto accommodate each cam followerSimilarly, the activation arm mounting body is configured to permit the activation armsto rotate distally from each pivot locationsuch as by providing a respective activation arm porton the distal side of each pivot locationThe cam follower portsand/or activation arm portsmay be dimensioned to prevent excessive motion of the activation armsif the activation ringbecomes detached from the activation arm mounting body.

In the shown example, the mechanism is configured such that all of the activation armsmove in unison at all times, thus ensuring that the device maintains a uniform generally circular shape during opening and closing. However, other embodiments may have features for adjusting the movement of, or disabling, one or more activation arms.

The membranesurrounds the activation arms, and extends from a proximal membrane endadjacent the activation assemblyto a distal membrane endadjacent to the distal arm endsThe membranecomprises a flexible material that is expandable to permit the distal arm endsto move from their respective first positions to their respective second positions. The membranemay be secured to the activation arms, but preferably is overmolded onto the activation arms. Overmolding can be accomplished by placing the assembled activation assemblyand activation armsinto a mold that receives the activation arms, and injecting the membrane material into the mold to surround each activation arm.

The membranemay comprise any suitable material that provides the desired degree of elongation. For example, the membranemay comprise a thermoplastic elastomer, and/or an elastomer based on styrenic olefinic rubber and hydrogenated isoprene, containing polypropylene as a reinforcing agent and mineral oil as a plasticizer and processing aid.

As shown in, the membranemay be molded to have a generally circular cross-sectional profile, as viewed along the longitudinal axisThe membranealso may be shaped to have a respective distinct riblocated at each activation arm, and a respective walllocated between each adjacent pair of activation arms. As shown in, each ribmay have a slightly larger diameter than the adjacent wallsbut this is not required. The ribsmay be molded to fully surround each, or they may only surround the respective outer radial surface(i.e., the side facing away from the longitudinal axis) of each. The membranemay extend fully from the activation assemblyto the distal arm endsand may include a lipthat wraps around the distal arm ends

The membranealso may include depth markers(see), which may be printed onto the membraneor formed as bumps or protrusions. The depth markersmay include numerical characters (e.g. numbers indicating dimensions or relative locations) or other shapes (e.g., letters) to identify a respective position of each depth markerThe depth markers also may comprises printed images or bumps/protrusions defined on the activation arms, that are visible through the membrane. Other alternatives and embodiments will be apparent to persons of ordinary skill in the art in view of the present disclosure.

The membranemay have any suitable dimensions. For example, the membranemay have a wall thickness of 0.024 inches to 0.008 inches, and more preferably of inches to 0.012 inches, and even more preferably of 0.015 inches to 0.017 inches. In one embodiment, the membranemay have a nominal wall thickness of 0.016 inches. It will be appreciated that these, and other dimensions herein, are subject to manufacturing tolerances, and the recitation of a specific number is intended to include typical variations due to manufacturing tolerances.

The membranealso may be selected to provide a desirable degree of expansion to allow the activation armsto open to the desired second arm positions. For example, the membranemay be selected such that it expands by at least 250% of its original circumference at the point of greatest elongation (typically the distal membrane end). More preferably, the membranemay be selected such that it expands by at least 300%, and even more preferably by 350% at the point of greatest elongation. This expansion is illustrated inas the change between membrane diameter MDat the distal membrane endinand the membrane diameter MDat the distal membrane endin.

The membranealso may have and suitable size for use as a brain retractor. For example, the membranemay have a contracted diameter of MDof 0.40 inches and an expanded diameter of 0.80 inches or more. In other cases, the membranemay have a contracted diameter of MDof 0.30 inches and an expanded diameter of 0.90inches or more. In still other cases, the membranemay have a contracted diameter of MDof 0.25 inches and an expanded diameter of 1.00 inches or more.

Referring back to, and also to, one or more of the activation armsmay include a light. The lightmay comprise a light emitting diode (LED), a terminal end of a light guide (e.g., a fiber optic cable), and so on. The activation armalso may be formed as a light guide that is optically connected to a remote light source. In the shown example one or more of the activation armsis formed of a transparent material (e.g., polycarbonate plastic), and has an LED lightlocated adjacent the distal arm endLight from the lightcan pass through the distal arm endto reach the surgery site. The distal arm endalso may be shaped or have surface treatments that help guide and distribute the light at the surgery site. Such shapes (e.g. Fresnel-type lenses or pyramidal bumps) and surface treatments for guiding and distributing light are known in the art.

The lightmay be mounted to an inner surface of the activation armor at other locations. Preferably, the lightis mounted in a light receiverthat is recessed into the activation arm. The activation armhas a slotthat leads to the light receiverThe slotis dimensioned to receive a light connector, such as a light guide or an electrical wire to power the light. In the shown example, the slotextends along the activation armfrom a proximal slot end′ to a distal slot end″ adjacent the light receiverThe proximal slot end′ may be located at or near the pivotor at any other location where access may be provided for a light connectorto enter the slot

The slotmay be located at any part of the activation arm, but preferably extends along the outer radial surfaceIn this case, the membranecan be overmolded over the outer radial surfacesuch that a portion of the ribis overmolded into the slotIn this case, the engagement between the membraneand the outer radial surfacehelps hold the ribat a fixed location as the activation armmoves to its second (expanded) position. When fully constructed, the membranealso encases the lightand the light connectorbetween the outer radial surfaceand, thus holding the lightin place during use and keeping the lightaway from contact with the brain tissue.

It will also be appreciated that one or more of the activation armsmay include a slotor other shapes for the purpose of receiving an overmolded part of the membrane(i.e., without a light), to enhance the connection between the activation armsand the membrane.

Referring now to, an exemplary introducerand its interaction with the remainder of the expandable access portis described in detail. The introducerextends from a proximal introducer endto a distal introducer endand has a tubular wallthat defines a cannulaThe cannulaextends along the longitudinal axisfrom the proximal introducer endto a point adjacent to the distal introducer endThe cannulaterminates at a probe tip receiverthat is configured to receive one or more different navigation probes. When fully inserted, the probe shaftextends along the cannulaand the probe tipseats in the probe tip receiverto hold the probe tipat a fixed location.